Solar eclipse flashback: When Madison astronomer thought he found new planet

Milwaukee Journal Sentinel

Golden leaves cover the ground in front of the renovated Washburn Observatory at the University of Wisconsin-Madison.

As millions of umbraphiles travel this weekend into the path of what's been dubbed the Great American Eclipse, a noteworthy eclipse-chaser and astronomer did pretty much the same thing 139 years ago.

James Watson was among the astronomers and scientists who traveled to America's West to observe a total solar eclipse in 1878, shortly before he was named the first director of the Washburn Observatory on the University of Wisconsin-Madison campus.

During the 1878 total solar eclipse, Watson, who by then had discovered comets and 22 asteroids, became convinced he glimpsed a new planet called Vulcan closer to the sun than Mercury.

Two decades earlier, a French mathematician who noticed unexplained peculiarities in Mercury's orbit declared a phantom planet named Vulcan was the reason for the movement of the smallest planet in our solar system. Then on July 29, 1878, Watson saw something he assumed was Vulcan as he witnessed the total solar eclipse in Wyoming.

At the time Watson was director of the University of Michigan observatory and a noted cosmic observer with a knack for discovering celestial bodies.

James C. Watson, director of the Washburn Observatory, thought he made an important discovery during the 1878 solar eclipse.

"He could apparently memorize star fields. He could look at a star field and the next time he looked at a telescope he could say – that wasn't there," said Jim Lattis, director of the University of Wisconsin-Madison Space Place.

Watson and one other astronomer thought they saw Vulcan during the 1878 eclipse, which was also noteworthy for Thomas Edison's efforts to invent a heat-detecting device called a tasimeter, which he tested during the eclipse. It didn't work. But undeterred, the inventor of the phonograph later created the light bulb.

Watson was so convinced the reddish star he glimpsed was Vulcan, he began building a special solar observatory when he was hired for the job in Madison. Wisconsin Gov. C.C. Washburn included $3,000 in the 1876 state budget to build a state-of-the-art observatory with a 15.6-inch telescope, then the third largest in the United States. Apparently Watson, who had written the definitive "Theoretical Astronomy," was highly sought after, akin to hiring a college football or basketball coach.

The solar observatory was a deep shaft dug in the side of the steep hill next to the Washburn Observatory that Watson thought could be used to safely observe the sun and hopefully detect Vulcan. The solar observatory was designed to look on either side of the sun in daytime, said Lattis. It didn't work.

"He thought he could isolate the sunlight by looking through a long tunnel with a mirror to point to one side of the sun or the other. I like to point to this as the beginning of innovative astronomical instruments at UW-Madison, though that was a failure," Lattis said.

Watson, who was born in Canada and moved to Michigan as a boy, didn't live to see Vulcan debunked. He died suddenly in Madison of peritonitis in 1880 at the age of 42. He bequeathed a large amount of money to create the James Craig Watson Medal, which is still awarded every two years by the National Academy of Sciences for contributions to astronomy.

The Washburn Observatory at the University of Wisconsin-Madison. Its first director, James Watson, thought he discovered a new planet during the solar eclipse of 1878.

The myth of Vulcan was finally put to rest in 1919 when another total solar eclipse was used to prove Einstein's theory of relativity, which helped explain why Mercury wobbles.

A lunar crater on the Moon is named for Watson.